There has been developed, for example, an ultrasonic motor using a piezoelectric vibrator, as a driving device for replacing an electromagnetic motor. There is also known an ultrasonic machine including processing means formed at an output end of the piezoelectric vibrator to perform various types of contact processing. Both the ultrasonic motor and the ultrasonic machine use vibration energy of the vibrator as a driving force or a processing force. In those cases, the piezoelectric vibrator forms a resonance state to obtain a large amplitude when applied with a voltage of a frequency of a natural mode of vibration, to thereby give the driving force or the processing force for rotation, direct operation, or the like to an opposite member that makes frictional contact with the piezoelectric vibrator. Ultrasonic vibrators and ultrasonic motors that utilize this principle are described in detail in Patent Documents 1 to 5, for example.
The piezoelectric vibrator as described above needs to be mechanically supported by some means in a support member for implementation. In this case, it is important for the support means to have small vibration energy loss and no change in vibration characteristics. Further, the ultrasonic motors and the ultrasonic machines generally bring the tip of the vibrator into pressure contact with the opposite member (transport member or work piece) to give a vibration energy of the vibrator as the driving force or the processing force to the opposite member. Therefore, a pressure mechanism for pressing the opposite member while holding the vibrator is necessary.
As an example of the conventional holding structure for the piezoelectric vibrator, Patent Document 1 discloses an ultrasonic motor having a structure in which the piezoelectric vibrator is accommodated and supported in a frame-shaped guide case to be slidable in a pressing direction, and the guide case is pressed in the pressing direction by spring means to thereby bring the piezoelectric vibrator into press contact with the opposite member.
Referring to FIG. 11, the structure of the ultrasonic motor is described. A rectangular piezoelectric vibrator 1 accommodated in a guide case 25 is supported at its two positions corresponding to node portions by guide portions 25a and 25b of the case 25, and a protruding portion 26 of an inner end surface of the guide case 25 is brought into contact with an end opposite to an output end 28 of the piezoelectric vibrator 1 via an elastic member 27. A side of the guide case 25 is supported by a guide plate 29 on a fixed side to be slidable, and an end of the guide case 25 is pressed by a coil spring 30, to thereby bring the output end 28 of the piezoelectric vibrator 1 into press contact with a member to be driven (driven member) 31.
With this structure, a voltage of a predetermined frequency is applied to excite vibration of the piezoelectric vibrator. Therefore, the piezoelectric vibrator simultaneously makes flexural vibration and stretching vibration so that the output end of the piezoelectric vibrator makes elliptical vibration to be periodically brought into press contact with the driven member. The frictional force between the piezoelectric vibrator and the driven member causes the driven member to perform operation such as rotation and direct operation.    Patent Document 1: JP 11-346486 A    Patent Document 2: JP 3311446 B2    Patent Document 3: JP 2004-297951 A    Patent Document 4: JP 2000-116162 A    Patent Document 5: JP 2005-65358 A    Patent Document 6: JP 2722211 B2